Differential-control magnet



Oct. 7 1924.

W. W. BCHER DIFFERENTIAL -CONTROL MAGNET Filed March 20. 1919 PatentedOct. 7, 1924.

UNITED -sTATEs PATENT OFFICE.

WILLIAM W. BCHER, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,TO KOHLER COMPANY, OF KOHLER, WISCONSIN, A CORPORATION OF WISCONSIN.

DIFFERENTIAL-CONTROL MAGNET.

Application led March 20, 1919. Serial No. 283,909.

To all whom t may concern:

Be it known that I, WILLIAM W. BCHER, citizenv of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented certain new and useful Improvements in Differential-ControlMagnets, of which the following is a speciiication.

My invention relates to improvements in i. differential control magnetsand it more especially consists of the features hereinafter pointed outin the annexed claims.

The purpose of this invention is to provide a super-sensitive magnetcontrol whose responsiveness is not jeopardized by the use of very heavycurrents to which the magnet may be subjected; to provide such arelation of parts that these ends will be brought about in a simple,compact and eicient man- I ner; to also provide a magnet that is readilyassemblable and which may use form-wound coils; and that will provide anefficient relation of parts comprised in the magnetic circuit so as toproduce the required initial I pull with very weak currents.

Withfthese and other ends in view I illustrate in the accompanyingdrawing such instances of adaptation as will disclose the fundamentallybroad features without limit- I ing myself to the specific detailsshown.

Fig. 1. is an elevation in section.

Fig. 2 is a diagram of related electric circuits, in series, forautomatically changing over the connections toprotect the sentitive lcoil from heavy currents.

Fig. 3 is a diagram similar to that shown in Fig. 2 showing the coilwindings in parallel relation to each other. i

Fig. 4 is a plan of a slotted insulating I washer.

Fig. 5 is an elevation in section of a modified core.

Magnets of the type disclosed herein are specially applicabley to theinitial controlof I isolated electric generating units in which theentire starting control current is of such small amperage that the tinewire coil must have many turns to concentrate enough iuX to energize themagnet to attract its armal@ ture.

The usual pivoted armatures are liable to stick, besides requiring anexcessive wattage in the coil to operate them. The type of startingcurrents mentioned and further exemplitied in my Patent #1,292,699 andan application Ser. 283,910 of March 20, 1919, are limited in amperesthrough the use of low voltage batteries of about 24 volts or even lessfor starting purposes. Such currents are caused to momentarily flow overthe usual service mains having normal or standard voltage currentconsuming devices connected thereto, at about 110 or 115 volts. Plantsof this kind must be started through the turning on of a single lamp ofsmall capacity but of the same voltage as that of the service mains.This means that the total wattage at the low voltage yof the batterywill be very small indeed. In order to respond to this delicate currentthe present magnet has been invented. It operates continuouslywithoutomissions, because the parts are simple and the moving portion isreduced to aI minimum weight.

The magnet windings comprise two formwound coils, the fine wire one, 24,terminating at and 36. The coarse wireU coil 31 has an inner terminal 33to which the outer end of the tine wire coil is attached. Its outerterminal is at 32. The line Wire coil 24 is separated from the core 6and the heavy winding 31 by insulation 25. This insulation is of theusual well known ilexible type and if desired the same may enclose theends of this coil, so that the coil can be passed into the otherwinding. When so assembled the two coils can be handled as a unit. Byinserting the core 6 within the yline wire coil 24 and placinginsulating washer. 26 on the core at the outer end of the coils and aniron head on shoulder 28, and insulating washers 21 and 2O and 5 on theinner or armature end of the coilsl and the flat iron ring 7 pressedonto the shoulder of this end of the core the coils with the assembledparts will constitute a unit.

The magnet units are held on iianged supports having the projecting rim3 formed of iron so as to coact with the iron head 7 to form an annularair gap 8 between them. The thick insulating washer 5 fits inside of therim or flange 3 where it is held by screws 4. This fastening in itselfwould not hold the outer heads in place so a thin iron casing 3() isplaced over the coils and also fastened by the screws 4. This casing hasa flange 29 that engages the outer iron head 27 so as to l hold all theparts against endwise displacement. t

l'llhe support 2 may be of any desired form and it may be attached to aninsulating base .1 or secured wherever desired, the only limitingcondition in practice being that ample provision be made adjacent thearmature stem 15 to accommodate the required electrical contacts whichare to be controlled by the. magnet.

This type of a magnet supplies an ideal magnetic circuit which insuresthe greatest possible sensitiveness of the moving parts of the system.rlrhe magnetic circuit of the combined coils is through the core 6,outer head 27, casing 30, flange 3, across air gap 8,'and over head 7onto the core at its armature end.

rl`he moving element of the magnet-or the armature, is made as light aspossible so as to be sensitive to the weakest currents used in the finewire coil. A guide stem 15 slides in a central hole 37 of the core 6. lthas a shoulder 12 against which a thin iron armature diaphragm 11 restswhile held by nut 13. The stem 15 is threaded at 14 up to the shoulder12 for nuts 12 and 17. The latter hold contact disk 15 in place on thestem at various distances from armature 11.

A clearance recess 9 is formed in the armature end of the core 6 toaccommodate, the shoulder 12 and thus admit the diaphragm 11 to approachthe flat ring 7 and the flange 3 as close as the paper or other thininsulation 10 will permit.

The armature 11, after having been initially moved into contact with theinsulation 10 remains in its attracted position principally through theresidual magnetism in' the adjacent iron parts. The entire magneticcircuit is then composed of highly permeable elements, since thediaphragm 11 spans the air gap 8. This insures steadiness of actionunder fluctuating current conditions in the magnet coils. As the coarsewire of coil 31 has but a few turns compared to fine wire coilI 24, atminimum currents within lts range the attraction of coil 31 will besmall. v r.

If the initial starting demand for current is greater than that requiredfor a single lamp the fine wire coil will be pro tected in any eventagainst overheating because the contact plate 15 will, as soon as thediaphragm 11 has been attracted, automatically cut in the coarse wirecoily 31 to carry the heavier current. When this has taken place thefine wire coil 24 may be entirely c'ut out or remain connected inparallel. Even if the coil 24 remains in parallel relation theImagnetism it can produce, on account of its high resistance will be Verysmall, in addition to that of coil 31, hence the residual magnetism ofthe parts plays a Y cooperative rle.'

The combined attraction of the two coils when they are in parallel, orof one coil alone, added to the residual effect is sufficient to holdthe diaphragm 11 attracted, under extremely Weak current-s, but theinitial magnetic flux would not be dense enough to produce the requiredmagnetism to raise the armature throughout its entire distance from aposition of rest. ln practice the relative resistance of the two coilshas been found to be approximately of the order, 445 to .075, though anyother working ratio may be employed according to the exigencies that mayarise whatever ratio is selected the armature 11 must instantly dropwhen current is cut off from either coil and it must also be instantlyattracted when the circuit is again closed but it must not drop underany other conditions.

The contact disk 15 is insulated from the threaded portion of the stem15 by bushings 16. lt coacts in its inner or upper position withcontacts 18 and inv its outer position with contacts 19. These contactsmaybe used for other purposes than those herein exemplied, or morecontacts and additional disks 15 may be used in any desired combinationso long as provision is made for the automatic connection of the coarsewire coil after the fine wire coil has performed its lfunction. v

The magnet heads 27 and 7 have insulating washers placed between themand the coils.- Next to permeable head 27 washer 26 is found. Next tothe armature end of the coil a washer 21 having an enlarged centralopening 22 and a tangential slot 23 to accommodate the initial end ofthe coarse wire coil, is placed. This is followed by a thin washer 20and a thick one, 5, to complete the insulation at this end of the coils.

It will be noted that on account of the carefully planned magneticcircuit a very dense field will be produced in the annular air gap 8,even with very weak currents.-

The diaphragm 11 is practically in parallel relation to the head 7 henceit becomes very responsive to the magnetic conditions ofthe air gapfield.

The circuits exemplified in Figs. 2 and 3 are jvholly suggestive as theymay be varied almost indefinitely. As instanced, 41 represents a motor.42 a battery or other source of current. 43 identifies service lamps, 44a lamp switch and 19 any desired connection to be controlled by the idleposition of the diaphragm, for instance the grounding of a magneto,etc.l

When the magnet is used on a base 1, the base may serve., as a stop tothe outward movement of the stem 15. The spring contacts 19 may servethe same purpose. The core 6 may have a hole throughout its length and along` stem 38 used instead of the short stem 15. Limit nuts 39 at theouter end of lll the stem will also serve as stops to limit the movementof the armature ll-away from the magnet.

If the magnet casing 30 and the connected parts with the coil terminalsprotruding through the slot 34 of the casing, be mounted vertically,gravity will in all ordinary cases serve to move the armature inopposition to the pull of the magnet, but if for any reason furtherassistance is required on account of another position of the magnet, orbecause of any other condition a coil spring 40 may be att-ached to stem15 or stem 38 at the bottom end, as suggested in Fig. 5.

What I claim is:- L

l. An electromagnet structure comprising a coil or coils constituting aunit having a core opening therethrough, a. rmeable core in suchopening, insulating eads adjacent the coil supported by the core, largeand reduced diameter permeable heads also supported by the core aflanged permeable support larger than the reduced diameter head so as toleave an air gap between the support -and the head, the said supportbeing atings are assembled, permeable heads at? tached to the core, anexternal permeable support adjacent one of the heads forming an air gapbetween the head and the support, a permeable diaphragm operable acrossthe air gap, means for controlling the movement of the diaphragm, apermeable casing surrounding the windings, a flange at one end of thesame adapted to engage the other head, and means for attaching the otherend of the casing to the support.

In testimony whereof I aix my signature.

WILLIAM W. BCHER.

